2.8 Complete head replacement on both cars

I have a 328xit with 30,000 miles and a 2008 528xi with 6,000 miles. When I took the 528 for service I mentioned an occasional tapping noise, No Big Deal. Two hours later I get a phone call that there is a design flaw and they are replacing the entire head. So I take the 328 to them, same thing. Two complete heads in one week, no questions asked. What is up with that? No recall?

bmw replaced the head on my 06 330i for they same simptoms, car had 22000 miles on it and i was told by the service writer that they had replaced heads on others, i live on the charlotte, nc. area.
Bob